GenerateRandomPointinaCircle.java

package medium;
/**
 * ClassName: GenerateRandomPointinaCircle.java
 * Author: chenyiAlone
 * Create Time: 2019/11/15 10:41
 * Description: No.478 Generate Random Point in a Circle
 *
 * Given the radius and x-y positions of the center of a circle, write a function randPoint which generates a uniform random point in the circle.
 *
 * Note:
 *
 * input and output values are in floating-point.
 * radius and x-y position of the center of the circle is passed into the class constructor.
 * a point on the circumference of the circle is considered to be in the circle.
 * randPoint returns a size 2 array containing x-position and y-position of the random point, in that order.
 * Example 1:
 *
 * Input:
 * ["Solution","randPoint","randPoint","randPoint"]
 * [[1,0,0],[],[],[]]
 * Output: [null,[-0.72939,-0.65505],[-0.78502,-0.28626],[-0.83119,-0.19803]]
 * Example 2:
 *
 * Input:
 * ["Solution","randPoint","randPoint","randPoint"]
 * [[10,5,-7.5],[],[],[]]
 * Output: [null,[11.52438,-8.33273],[2.46992,-16.21705],[11.13430,-12.42337]]
 * Explanation of Input Syntax:
 *
 * The input is two lists: the subroutines called and their arguments. Solution's constructor has three arguments, the radius, x-position of the center, and y-position of the center of the circle. randPoint has no arguments. Arguments are always wrapped with a list, even if there aren't any.
 *
 */
public class GenerateRandomPointinaCircle {
    
    private double x, y, radius;
    
    /**
     * Your Solution object will be instantiated and called as such:
     * Solution obj = new Solution(radius, x_center, y_center);
     * double[] param_1 = obj.randPoint();
     */
    public GenerateRandomPointinaCircle(double radius, double x_center, double y_center) {
        this.x = x_center;
        this.y = y_center;
        this.radius = radius;
    }

    public double[] randPoint() {
        double[] ret = new double[2];
        ret[0] = x - radius + Math.random() * (2 * radius);
        ret[1] = y - radius + Math.random() * (2 * radius);
        if (Math.pow(ret[0] - x, 2) + Math.pow(ret[1] - y, 2) > Math.pow(radius, 2))
            return randPoint();
        return ret;
    }
    
}